1. Field of the Invention
The present invention relates to a reflection type liquid crystal display.
2. Description of the Related Art
In recent years, a reflection type liquid crystal display (LCD) has been developed in which incident light from an observer side is reflected by a reflective display electrode so that display is observed.
FIG. 2 is a plan view showing a display pixel and nearby area of an example of the above mentioned reflective type LCD. FIG. 3 is a cross sectional view, along the line Axe2x80x94A in FIG. 2, showing manufacturing steps.
As shown in FIG. 2, a TFT is formed in an area close to a crossing point between a gate signal line 51 and a drain signal line 52. The gate signal line 51 includes a gate electrode 11 and supplies a gate signal to a gate, while the drain signal line 52 includes a drain electrode 16 and supplies a drain signal to a drain. The gate 11 of the TFT is connected to the gate signal line 51. The drain 13d is connected to the drain signal line 52, while the source 13s is connected to a reflection display electrode 28.
The reflection display electrode 28 preferably has an uneven surface, rather than an even surface, so that incident light can be reflected in multiple directions. With such an arrangement, the display of the reflection type LCD (Liquid Crystal Display) can be observed from a larger area, so that a larger viewing angle can be ensured.
Referring to FIGS. 3(a) to 3(d), an example of manufacturing steps for the above described reflection type LCD will be described.
Step 1 (FIG. 3(a)): on an insulating substrate 10, there are sequentially formed a first gate electrode 11, a gate insulating film 12, and an active layer 13, wherein the insulating substrate 10 comprises a quartz glass, a non-alkali glass, and so on, the first gate electrode 11 comprises a refractory metal (Cr, Mo, and so on), the gate insulating film 12 comprises a SiN film and a SiO2 film, and the active layer 13 comprises an island-shaped polycrystalline silicon film.
Then, in the active layer 13, there are formed a channel 13c above the first gate electrode 11, and a source 13s and a drain 13d at the respective sides of the channel 13c, wherein the source 13s and the drain 13d are formed through ion implantation.
Further, on the channel 13c, there is formed a stopper insulating film 14, comprising a SiO2 film, as a mask covering the channel 13c for preventing ion intrusion at the time of ion implantation.
Covering the entire surface of the gate insulating film 12, the active layer 13, and the stopper insulating film 14, there is formed an interlayer insulating film 15, comprising laminated SiO2 film, SiN film and SiO2 film.
Then, contact holes 16, 17 are made in the interlayer insulating film 15 at respective positions corresponding to the drain 13d and the source 13s. The contact hole 16, corresponding to the drain 13d, is filled by metal, specifically, by a single Al layer or sequentially laminated Mo and Al layers, thereby forming a drain electrode 18. At the same time of the formation of the drain electrode 18, a second gate electrode 19 is formed on the interlayer insulating film 15 above the channel 13c using metal, specifically, a single Al layer or sequentially laminated Mo and Al layers. Note that nothing is filled in the contact hole 17.
The second gate electrode 19 is connected to the gate signal line 51 on the insulating substrate 10, via a contact hole 20, formed in the gate insulating film 12 and the interlayer insulating film 15 as shown in FIG. 1. A drain signal line 52 is formed on the interlayer insulating film 15.
Step 2 (FIG. 3(b)): a first planarization insulating film 21, made of organic resin, and so on, is formed over the layers formed at Step 1, and a first resist film 22 is applied thereon. Thereafter, exposure and development processes are applied using a first mask 23, which has an opening at a position corresponding to the contact hole 17, followed by etching the first planarization insulating film 21, thereby forming a contact hole 24 corresponding to the contact hole 17.
Step 3 (FIG. 3(c)): a second planarization insulating film 25 is formed on the semiconductor film 13 in the contact hole 24 and the exposed first planarization insulating film 21. A second resist film 26 is then applied on the film 25. Thereafter, exposure and development processes are applied using a second mask 32, which has an opening at a position corresponding to a recess 27 (29) which is to be formed on an area, on the second planarization insulating film 25, where a reflection display electrode 28 is to be formed, and the second planarization insulating film 25 is thereafter etched whereby a concave 29 (27) is formed (FIG. 3(d)).
With the second resist film 26 subsequently removed, a contact hole 24, where the reflection display electrode 28 contacts the source 13s, is formed, and so are concaves 29 (27) in the reflection display electrode formation area. With the above, the reflection display electrode 28 resultantly has an uneven surface. As a result, incident light can be reflected in multiple directions, and a wider viewing angle can thus be achieved.
However, the above described manufacturing method of a reflection type LCD may result in increased costs and labor as it initially requires formation of a contact hole 24 in the first planarization insulating film 21, and then formation of a second planarization insulating film 25 in a different manufacturing step for subsequent formation of a concave 29 (27) therein.
The present invention aims to provide an efficient method for manufacturing a reflection type LCD having a concave in a reflection film.
According to the present invention, two exposures are applied to a photosensitive resin, using two different masks, before development, whereby two types of concaves each having different depths are formed. This enables reduction of the number of steps in formation of concave with two different depths.
In particular, a concave with one of the two depths is used to constitute a contact hole for connection between a TFT transistor and a reflection film (a reflection electrode) having a size corresponding to a pixel, and a concave with another depth is used as a concave in the reflection electrode.